High accuracy and precision alignment is highly desirable or essential in innumerable fields of endeavor. Many techniques for attempting such alignment are known. For example, a number of techniques for various applications monitor the position of one or more reflections off the object(s) to be alignment to determine alignment. However, heretofore these reflections obeyed the principal that the angle of reflection (arbitrarily defined as being in a positive direction from the normal to the object's surface) was equal to the angle of incidence but in the negative direction to the normal. As a result, these techniques generally had to utilize complicated and costly schemes that yielded alignment information whose accuracy and precision was limited.
I have found a device and method for alignment employing a relatively recently discovered class of materials known as phase conjugators. Phase conjugate materials provide reflection along the incident path. (A good discussion of phase conjugation and materials exhibiting such properties in the optical region of the electromagnetic spectrum is furnished in the article by Shkunov and Zel'dovich, Optical Phase Conjugation, Scientific American, pp. 54-59 Dec. 1985))
Phase conjugation has been shown to be useful for several applications, particularly in the optical region of the electromagnetic spectrum, as explained in the article by Peper, Applications of Optical Phase Conjugation, Scientific American, pp. 74-83, (Jan. 1986). Perhaps the most common application has been to correct distortions arising in a coherent light beam as the beam lases in an optical cavity. U.S. Pat. No. 4,529,273 and the article by Lindsay and Dainty, Partial Cancellation of Specular Refraction in the Presence of a Phase-Conjugate Mirror, Optics Communications, Vol. 59, No. 5,6, pp. 405-410 (Oct. 1, 1986), both disclose so-called phase conjugate reflector or phase conjugate mirror ("PCM") configurations for correction of these optical distortions.
Optical phase conjugators may also be used to construct optical inertial navigation sensors such as the gyroscope described in U.S. Pat. No. 4,681,446 and the accelerometer described in U.S. Pat. No. 4,640,618, and to construct an optical interferometer for determination of surface deformations as described in U.S. Pat. No. 4,280,764. None of these patents or the previously mentioned articles illustrate or suggest using PCMs in configurations and with methods that yield highly accurate and precise alignment information.